Decriminalizing an illegal market may be a useful strategy for reducing crime. It is also necessary, however, to have a clear understanding of the nature of the illegal market before undertaking such an endeavor. Experiences in the Netherlands show that decriminalizing illegal markets may indeed result in a substantial reduction of organized crime and other criminal activities, if the regulatory system is designed adequately. These experiences also show that such systems inherently lack flexibility and that criminals are usually quick to re-enter the market when unforeseen developments, particularly technical innovations and internationalization, create new illegal business opportunities.